Imaging device and digital camera using the imaging device

ABSTRACT

An imaging device has a zoom lens system having a plurality of lens units and forming an optical image of an object so as to continuously optically zoom by varying distances between the lens unit; and an image sensor converting the optical image formed by the zoom lens system to an electric signal. The zoom lens system has from an object side: a first lens unit being overall negative and including a reflecting surface that bends a luminous flux substantially 90 degrees; and a second lens unit disposed with a variable air distance from the first lens unit, and having a negative optical power.

[0001] RELATED APPLICATION

[0002] This application is based on application No. 2002-196171 filed in Japan on Jul. 4, 2002, the content of which is hereby incorporated by reference.

[0003] 1. Field of the Invention

[0004] The present invention relates to an imaging device having an image sensor that converts, to electric signals, optical images formed on the light receiving surface of a charge coupled device (CCD), a complementary metal-oxide semiconductor (CMOS) sensor or the like, and more particularly, to an imaging device which is a principal element of cameras incorporated in or externally attached to digital cameras, personal computers, mobile computers, mobile telephones, personal digital assistances (PDAs) and the like. Specifically, the present invention relates to a compact imaging device having a zoom lens system.

[0005]2. Description of the Prior Art

[0006] In recent years, digital cameras have been rapidly becoming widespread that convert an optical image to electronic signals by using an image sensor such as a CCD or a CMOS sensor instead of silver halide film, convert the data to digital form, and record or transfer the digitized data. In such digital cameras, since CCDs and CMOS sensors having high pixels such as two million pixels and three million pixels are comparatively inexpensively provided recently, a high-performance imaging device mounted with an image sensor is in greatly increasing demand. In particular, a compact imaging device is desired that is provided with a zoom lens system capable of performing zooming without any image quality degradation.

[0007] Further, in recent years, imaging devices have been becoming incorporated in or externally attached to personal computers, mobile computers, mobile telephones, PDAs and the like because of improvements in the image processing capability of semiconductor elements and the like, which spurs the demand for a high-performance imaging device.

[0008] As zoom lens systems used for such imaging devices, so-called minus lead zoom lens systems in which the lens unit disposed on the most object side has a negative optical power are proposed in large numbers. Minus lead zoom lens systems have features such that they are easily made wide-angle and that the lens back focal length necessary for inserting an optical low-pass filter is easily secured.

[0009] Conventional examples of minus lead zoom lens systems include zoom lens systems proposed as taking lens systems for film-based cameras. However, in these zoom lens systems, since the exit pupil of the lens system in the shortest focal length condition is situated comparatively near the image plane, it does not match with the pupil of the microlens provided so as to correspond to each pixel of the image sensor having high pixels, so that a sufficient quantity of peripheral light cannot be secured. In addition, since the position of the exit pupil largely varies during zooming, the setting of the pupil of the microlens is difficult. Further, since required optical performance such as spatial frequency characteristics is completely different between silver halide film and image sensors to begin with, optical performance required of image sensors cannot be sufficiently secured. For these reasons, there has emerged a need for the development of a dedicated zoom lens system optimized for imaging devices having an image sensor.

[0010] On the other hand, to reduce the size of the imaging device, a proposal has been made to attain size reduction without any change in optical path length by bending the zoom lens system in the middle of the optical path. For example, Japanese Laid-Open Patent Application No. H11-196303 proposes an imaging device where in a minus lead zoom lens system, a reflecting surface is provided on the optical path and the optical path is bent substantially 90 degrees by the reflecting surface and then forms an optical image on the image sensor by way of movable lens units. The imaging device disclosed by this application has a structure that a reflecting surface is provided on the image side of a fixed lens element of a negative meniscus configuration and the optical path is bent substantially 90 degrees by the reflecting surface and then reaches the image sensor by way of two movable positive lens units and a fixed positive lens unit.

[0011] As another example, Japanese Laid-Open Patent Application No. H11-258678 discloses a structure that a reflecting surface is provided on the image side of a fixed lens element of a negative meniscus configuration and a movable positive lens unit and the optical path is bent substantially 90 degrees by the reflecting surface and then reaches the image sensor by way of a positive lens unit.

[0012] However, in these two applications, only the lens barrel structure is disclosed and no specific zoom lens system structure is shown. It is difficult to reduce the overall size of imaging devices having a zoom lens system unless the zoom lens system taking up the largest space in volume is optimized.

OBJECT AND SUMMARY

[0013] An object of the present invention is to provide an improved imaging device.

[0014] Another object of the present invention is to provide an imaging device being compact although having a high-performance and high-magnification zoom lens system.

[0015] The above-mentioned objects are attained by an imaging device having the following structure:

[0016] An imaging device comprising: a zoom lens system having a plurality of lens units and forming an optical image of an object so as to continuously optically zoom by varying distances between the lens unit; and an image sensor converting the optical image formed by the zoom lens system to an electric signal, wherein the zoom lens system comprises from an object side: a first lens unit being overall negative and including a reflecting surface that bends a luminous flux substantially 90 degrees; and a second lens unit disposed with a variable air distance from the first lens unit, and having a negative optical power.

[0017] Moreover, another aspect of the present invention is a digital camera including the above-described imaging device. While the term digital camera conventionally denotes cameras that record only optical still images, cameras that can handle moving images as well and home digital video cameras have also been proposed and at present, there is no distinction between cameras that record only still images and cameras that can handle moving images as well. Therefore, in the following description, the term digital camera includes all of the cameras such as digital still cameras and digital movie cameras where an imaging device having an image sensor that converts optical images formed on the light receiving surface of the image sensor to electric signals is a principal element.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] This and other objects and features of this invention will become clear from the following description, taken in conjunction with the preferred embodiments with reference to the accompanied drawings in which:

[0019]FIG. 1 is a lens construction view of a first embodiment (first example);

[0020]FIG. 2 is a lens construction view of a second embodiment (second example);

[0021]FIG. 3 is a lens construction view of a third embodiment (third example);

[0022]FIG. 4 is a lens construction view of a fourth embodiment (fourth example);

[0023]FIG. 5 is a lens construction view of a fifth embodiment (fifth example);

[0024]FIG. 6 is a lens construction view of a sixth embodiment (sixth example);

[0025]FIG. 7 is a lens construction view of a seventh embodiment (seventh example);

[0026]FIG. 8 is a lens construction view of an eighth embodiment (eighth example);

[0027]FIG. 9 is a lens construction view of a ninth embodiment (ninth example);

[0028]FIG. 10 is a lens construction view of a tenth embodiment (tenth example);

[0029]FIGS. 11A to 11I are graphic representations of aberrations of the first embodiment in in-focus state at infinity;

[0030]FIGS. 12A to 12I are graphic representations of aberrations of the second embodiment in in-focus state at infinity;

[0031]FIGS. 13A to 13I are graphic representations of aberrations of the third embodiment in in-focus state at infinity;

[0032]FIGS. 14A to 14I are graphic representations of aberrations of the fourth embodiment in in-focus state at infinity;

[0033]FIGS. 15A to 15I are graphic representations of aberrations of the fifth embodiment in in-focus state at infinity;

[0034]FIGS. 16A to 16I are graphic representations of aberrations of the sixth embodiment in in-focus state at infinity;

[0035]FIGS. 17A to 17I are graphic representations of aberrations of the seventh embodiment in in-focus state at infinity;

[0036]FIGS. 18A to 18I are graphic representations of aberrations of the eighth embodiment in in-focus state at infinity;

[0037]FIGS. 19A to 19I are graphic representations of aberrations of the ninth embodiment in in-focus state at infinity;

[0038]FIGS. 20A to 20I are graphic representations of aberrations of the tenth embodiment in in-focus state at infinity;

[0039]FIG. 21 is a construction view showing the present invention in outline; and

[0040]FIG. 22 is a construction view showing the use condition of the present invention in the shortest focal length condition.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0041] Referring to the drawings, an embodiment of the present invention will be described.

[0042] An imaging device according to the embodiment of the present invention comprises, for example as shown in FIG. 21, from the object side (subject side): a zoom lens system TL forming an optical image of an object so as to zoom, an optical low-pass filter LPF, and an image sensor SR converting the optical image formed by the zoom lens system TL to electric signals. The zoom lens system comprises a first lens unit Gr1 including a prism PR having a reflecting surface inside, and succeeding lens units. The imaging device is a principal element of cameras incorporated in or externally attached to digital cameras, video cameras, personal computers, mobile computers, mobile telephones, PDAs and the like.

[0043] The zoom lens system TL comprises a plurality of lens units including the first lens unit Gr1. The size of the optical image can be varied by varying the distances between the lens units. The first lens unit Gr1 has a negative optical power, and includes the prism PR that bends the optical axis of the object light substantially 90 degrees.

[0044] The optical low-pass filter LPF has a specific cutoff frequency for adjusting the spatial frequency characteristics of the taking lens system to thereby eliminate the color moire generated in the image sensor. The optical low-pass filter of the embodiment is a birefringent low-pass filter formed by laminating a birefringent material such as crystal having its crystallographic axis adjusted in a predetermined direction, wave plates changing the plane of polarization, or the like. As the optical low-pass filter, a phase low-pass filter or the like may be adopted that attains necessary optical cutoff frequency characteristics by a diffraction effect.

[0045] The image sensor SR comprises a CCD having a plurality of pixels, and converts the optical image formed by the zoom lens system to electric signals by the CCD. The signals generated by the image sensor SR undergo predetermined digital image processing or image compression processing as required, and are recorded into a memory (a semiconductor memory, an optical disk, etc.) as digital video signals or in some cases, transferred to another apparatus through a cable or by being converted to infrared signals. A CMOS sensor may be used instead of a CCD.

[0046] FIGS. 1 to 10 are construction views showing the lens arrangements, in the shortest focal length condition, of the zoom lens systems included in imaging devices according to a first to a tenth embodiment of the present invention. In these figures, the prism PR having an internal reflection surface is illustrated as a plane-parallel plate, and the optical path is illustrated as a straight line.

[0047] A zoom lens system of the first embodiment comprises from the object side to the image side: a first lens unit Gr1 including a first lens element L1 being a negative meniscus lens element convex to the object side, and a plate PR corresponding to the prism; a second lens unit Gr2 including a second lens element L2 of a bi-concave configuration and a third lens element L3 of a positive meniscus configuration convex to the object side; a diaphragm ST; a third lens unit Gr3 including a first doublet lens element DL1 consisting of a fourth lens element L4 of a bi-convex configuration and a fifth lens element L5 of a bi-concave configuration; a fourth lens unit Gr4 including a sixth lens element L6 of a positive meniscus configuration concave to the object side; and a fifth lens unit Gr5 including a seventh lens element L7 of a negative meniscus configuration concave to the object side. On the image side of the fifth lens unit Gr5 of this zoom lens system, a plane-parallel plate LPF corresponding to the optical low-pass filter is disposed. In this embodiment, the first lens unit Gr1 and the second lens unit Gr2 have a negative optical power, the third lens unit Gr3 and the fourth lens unit Gr4 have a positive optical power, and the fifth lens unit Gr5 has a negative optical power.

[0048] In this zoom lens system, in zooming from the shortest focal length condition to the longest focal length condition, the first lens unit Gr1 is fixed with respect to the image plane, the second lens unit Gr2 moves so as to draw a locus of a U-turn convex to the image side such that it first moves toward the image side and then moves toward the object side, the third lens unit Gr3 substantially monotonously moves toward the object side integrally with the diaphragm ST disposed on the object side of the third lens unit Gr3, the fourth lens unit Gr4 substantially monotonously moves toward the image side, and the fifth lens unit Gr5 is fixed with respect to the image plane with the plane-parallel plate LPF disposed on the image side of the fifth lens unit Gr5.

[0049] Of the surfaces of the lens elements, both side surfaces of the second lens element L2, the image side surface of the sixth lens element L6 and the object side surface of the seventh lens element L7 are aspherical.

[0050]FIG. 22 is a construction view showing the use condition, in the shortest focal length condition, of the zoom lens system of the first embodiment. As mentioned above, the optical axis of the first lens element L1 being a negative meniscus lens element convex to the object side, or the optical axis OAX of the object light, and the optical axis of the prism PR, or the optical axis IAX of the image light, form an angle of 90 degrees. With this construction, an imaging device being extremely thin in the direction of the optical axis OAX of the object side can be structured.

[0051] A zoom lens system of the second embodiment comprises from the object side to the image side: a first lens unit Gr1 including a first lens element L1 being a negative meniscus lens element convex to the object side, a plate PR corresponding to the prism, and a second lens element L2 of a positive meniscus configuration convex to the object side; a second lens unit Gr2 including a third lens element L3 of a negative meniscus configuration convex to the object side and a fourth lens element L4 of a positive meniscus configuration convex to the object side; a diaphragm ST; a third lens unit Gr3 including a first doublet lens element DL1 consisting of a fifth lens element L5 of a bi-convex configuration and a sixth lens element L6 of a bi-concave configuration; a fourth lens unit Gr4 including a seventh lens element L7 of a positive meniscus configuration concave to the object side; and a fifth lens unit Gr5 including an eighth lens element L8 of a negative meniscus configuration convex to the object side. On the image side of the fifth lens unit Gr5 of this zoom lens system, a plane-parallel plate LPF corresponding to the optical low-pass filter is disposed. In this embodiment, the first lens unit Gr1 and the second lens unit Gr2 have a negative optical power, the third lens unit Gr3 and the fourth lens unit Gr4 have a positive optical power, and the fifth lens unit Gr5 has a negative optical power.

[0052] In this zoom lens system, in zooming from the shortest focal length condition to the longest focal length condition, the first lens unit Gr1 is fixed with respect to the image plane, the second lens unit Gr2 moves so as to draw a locus of a U-turn convex to the image side such that it first moves toward the image side and then moves toward the object side, the third lens unit Gr3 substantially monotonously moves toward the object side integrally with the diaphragm ST disposed on the object side of the third lens unit Gr3, the fourth lens unit Gr4 substantially monotonously moves toward the image side, and the fifth lens unit Gr5 is fixed with respect to the image plane together with the plane-parallel plate LPF disposed on the image side of the fifth lens unit Gr5.

[0053] Of the surfaces of the lens elements, the object side surface of the first lens element L1, both side surfaces of the third lens element L3, the image side surface of the seventh lens element L7 and the object side surface of the eighth lens element are aspherical.

[0054] A zoom lens system of the third embodiment comprises from the object side to the image side: a first lens unit Gr1 including a first lens element L1 being a negative meniscus lens element convex to the object side, and a plate PR corresponding to the prism; a second lens unit Gr2 including a second lens element L2 of a negative meniscus configuration convex to the object side and a third lens element L3 of a positive meniscus configuration convex to the object side; a diaphragm ST; a third lens unit Gr3 including a first doublet lens element DL1 consisting of a fourth lens element L4 of a bi-convex configuration and a fifth lens element L5 of a bi-concave configuration; a fourth lens unit Gr4 including a sixth lens element L6 of a positive meniscus configuration concave to the object side; and a fifth lens unit Gr5 including a seventh lens element L7 of a negative meniscus configuration convex to the object side. On the image side of the fifth lens unit Gr5 of this zoom lens system, a plane-parallel plate LPF corresponding to the optical low-pass filter is disposed. In this embodiment, the first lens unit Gr1 and the second lens unit Gr2 have a negative optical power, the third lens unit Gr3 and the fourth lens unit Gr4 have a positive optical power, and the fifth lens unit Gr5 has a negative optical power.

[0055] In this zoom lens system, in zooming from the shortest focal length condition to the longest focal length condition, the first lens unit Gr1 is fixed with respect to the image plane, the second lens unit Gr2 moves so as to draw a locus of a U-turn convex to the image side such that it first moves toward the image side and then moves toward the object side, the third lens unit Gr3 substantially monotonously moves toward the object side integrally with the diaphragm ST disposed on the object side of the third lens unit Gr3, the fourth lens unit Gr4 substantially monotonously moves toward the image side, and the fifth lens unit Gr5 is fixed with respect to the image plane together with the plane-parallel plate LPF disposed on the image side of the fifth lens unit Gr5.

[0056] Of the surfaces of the lens elements, both side surfaces of the second lens element L2, the image side surface of the fifth lens element L5 and both side surfaces of the sixth lens element L6 are aspherical.

[0057] A zoom lens system of the fourth embodiment comprises from the object side to the image side: a first lens unit Gr1 including a first lens element L1 being a negative meniscus lens element convex to the object side, and a plane PR corresponding to the prism; a second lens unit Gr2 including a second lens element L2 of a negative meniscus configuration convex to the object side and a third lens element L3 of a positive meniscus configuration convex to the object side; a diaphragm St; a third lens unit Gr3 including a fourth lens element L4 of a bi-convex configuration and a first doublet lens element DL1 consisting of a fifth lens element L5 of a positive meniscus configuration concave to the object side and a sixth lens element L6 of a negative meniscus configuration concave to the object side; and a fourth lens unit Gr4 including a seventh lens element L7 of a bi-convex configuration. On the image side of the fourth lens unit Gr4 of this zoom lens system, a plane-parallel plate LPF corresponding to the optical low-pass filter is disposed. In this embodiment, the first lens unit Gr1 and the second lens unit Gr2 have a negative optical power, and the third lens unit Gr3 and the fourth lens unit Gr4 have a positive optical power.

[0058] In this zoom lens system, in zooming from the shortest focal length condition to the longest focal length condition, the first lens unit Gr1 is fixed with respect to the image plane, the second lens unit Gr2 moves so as to draw a locus of a U-turn convex to the image side such that it first moves toward the image side and then moves toward the object side, the third lens unit Gr3 substantially monotonously moves toward the object side integrally with the diaphragm ST disposed on the object side of the third lens unit Gr3, the fourth lens unit Gr4 substantially monotonously moves toward the image side, and the plane-parallel plate LPF is fixed with respect to the image plane.

[0059] Of the surfaces of the lens elements, both side surfaces of the second lens element L2, the image side surface of the sixth lens element L6 and the both side surfaces of the seventh lens element L7 are aspherical.

[0060] A zoom lens system of the fifth embodiment comprises from the object side to the image side: a first lens unit Gr1 including a first lens element L1 being a negative meniscus lens element concave to the object side, and a plate PR corresponding to the prism; a second lens unit Gr2 including a second lens element L2 of a negative meniscus configuration convex to the object side and a third lens element L3 of a positive meniscus configuration convex to the object side; a diaphragm ST; a third lens unit Gr3 including a first doublet lens element DL1 consisting of a fourth lens element L4 of a bi-convex configuration and a fifth lens element L5 of a bi-concave configuration; and a fourth lens unit Gr4 including a sixth lens element L6 of a positive meniscus configuration convex to the object side. On the image side of the fourth lens unit Gr4 of this zoom lens system, a plane-parallel plate LPF corresponding to the optical low-pass filter is disposed. In this embodiment, the first lens unit Gr1 and the second lens unit Gr2 have a negative optical power, and the third lens unit Gr3 and the fourth lens unit Gr4 have a positive optical power.

[0061] In this zoom lens system, in zooming from the shortest focal length condition to the longest focal length condition, the first lens unit Gr1 is fixed with respect to the image plane, the second lens unit Gr2 moves so as to draw a locus of a U-turn convex to the image side such that it first moves toward the image side and then moves toward the object side, the third lens unit Gr3 substantially monotonously moves toward the object side integrally with the diaphragm ST disposed on the object side of the third lens unit Gr3, the fourth lens unit Gr4 substantially monotonously moves toward the image side, and the plane-parallel plate LPF is fixed with respect to the image plane.

[0062] Of the surfaces of the lens elements, both side surfaces of the second lens element L2, the image side surface of the fifth lens element L5 and the both side surfaces of the sixth lens element L6 are aspherical.

[0063] A zoom lens system of the sixth embodiment comprises from the object side to the image side: a first lens unit Gr1 including a first lens element L1 being a negative meniscus lens element convex to the object side, and a plate PR corresponding to the prism; a second lens unit Gr2 including a second lens element L2 of a negative meniscus configuration convex to the object side and a third lens element L3 of a positive meniscus configuration convex to the object side; a diaphragm ST; a third lens unit Gr3 including a first doublet lens element DL1 consisting of a fourth lens element L4 of a bi-convex configuration and a fifth lens element L5 of a bi-concave configuration; and a fourth lens unit Gr4 including a sixth lens element L6 of a negative meniscus configuration concave to the object side. On the image side of the fourth lens unit Gr4 of this zoom lens system, a plane-parallel plate LPF corresponding to the optical low-pass filter is disposed. In this embodiment, the first lens unit Gr1 and the second lens unit Gr2 have a negative optical power, and the third lens unit Gr3 and the fourth lens unit Gr4 have a positive optical power.

[0064] In this zoom lens system, in zooming from the shortest focal length condition to the longest focal length condition, the first lens unit Gr1 is fixed with respect to the image plane, the second lens unit Gr2 moves so as to draw a locus of a U-turn convex to the image side such that it first moves toward the image side and then moves toward the object side, the third lens unit Gr3 substantially monotonously moves toward the object side integrally with the diaphragm ST disposed on the object side of the third lens unit Gr3, the fourth lens unit Gr4 substantially monotonously moves toward the image side, and the plane-parallel plate LPF is fixed with respect to the image plane.

[0065] Of the surfaces of the lens elements, both side surfaces of the second lens element L2, the image side surface of the fifth lens element L5 and the both side surfaces of the sixth lens element L6 are aspherical.

[0066] A zoom lens system of the seventh embodiment comprises from the object side to the image side: a first lens unit Gr1 including a fist lens element L1 being a negative meniscus lens element convex to the object side, a second lens element L2 of a positive meniscus configuration convex to the object side, and a plane PR corresponding to the prism; a second lens unit Gr2 including a third lens element L3 of a negative meniscus configuration convex to the object side and a fourth lens element L4 of a positive meniscus configuration convex to the object side; a diaphragm ST; a third lens unit Gr3 including a first doublet lens element DL1 consisting of a fifth lens element L5 of a bi-convex configuration and a sixth lens element L6 of a bi-concave configuration; and a fourth lens unit Gr4 including a seventh lens element L7 of a negative meniscus configuration concave to the object side. On the image side of the fourth lens unit Gr4 of this zoom lens system, a plane-parallel plate LPF corresponding to the optical low-pass filter is disposed. In this embodiment, the first lens unit Gr1 and the second lens unit Gr2 have a negative optical power, and the third lens unit Gr3 and the fourth lens unit Gr4 have a positive optical power.

[0067] In this zoom lens system, in zooming from the shortest focal length condition to the longest focal length condition, the first lens unit Gr1 is fixed with respect to the image plane, the second lens unit Gr2 moves so as to draw a locus of a U-turn convex to the image side such that it first moves toward the image side and then moves toward the object side, the third lens unit Gr3 substantially monotonously moves toward the object side integrally with the diaphragm ST disposed on the object side of the third lens unit Gr3, the fourth lens unit Gr4 substantially monotonously moves toward the image side, and the plane-parallel plate LPF is fixed with respect to the image plane.

[0068] Of the surfaces of the lens elements, the image side surface of the third lens element L3, the image side surface of the fourth lens element L4, the image side surface of the sixth lens element L6 and both side surfaces of the seventh lens element L7 are aspherical.

[0069] A zoom lens system of the eighth embodiment comprises from the object side to the image side: a first lens unit Gr1 including a first lens element L1 being a negative meniscus lens element convex to the object side and a plane PR corresponding to the prism; a second lens unit Gr2 including a second lens element L2 of a bi-concave configuration and a third lens element L3 of a positive meniscus configuration convex to the object side; a diaphragm ST; a third lens unit Gr3 including a first doublet lens element DL1 consisting of a fourth lens element L4 of a bi-convex configuration and a fifth lens element L5 of a bi-concave configuration, and a sixth lens element L6 of a negative meniscus configuration convex to the object side; and a fourth lens unit Gr4 including a seventh lens element L7 of a negative meniscus configuration concave to the object side. On the image side of the fourth lens unit Gr4 of this zoom lens system, a plane-parallel plate LPF corresponding to the optical low-pass filter is disposed. In this embodiment, the first lens unit Gr1 and the second lens unit Gr2 have a negative optical power, and the third lens unit Gr3 and the fourth lens unit Gr4 have a positive optical power.

[0070] In this zoom lens system, in zooming from the shortest focal length condition to the longest focal length condition, the first lens unit Gr1 is fixed with respect to the image plane, the second lens unit Gr2 moves so as to draw a locus of a U-turn convex to the image side such that it first moves toward the image side and then moves toward the object side, the third lens unit Gr3 substantially monotonously moves toward the object side integrally with the diaphragm ST disposed on the object side of the third lens unit Gr3, the fourth lens unit Gr4 substantially monotonously moves toward the image side, and the plane-parallel plate LPF is fixed with respect to the image plane.

[0071] Of the surfaces of the lens elements, the image side surface of the second lens element L2, the image side surface of the third lens element, the image side surface of the sixth lens element L6 and both side surfaces of the seventh lens element L7 are aspherical.

[0072] A zoom lens system of the ninth embodiment comprises from the object side to the image side: a first lens unit Gr1 including a first lens element L1 being a negative meniscus lens element convex to the object side, a second lens element L2 of a positive meniscus configuration convex to the object side, and a plane PR corresponding to the prism; a second lens unit Gr2 including a third lens element L3 of a bi-concave configuration and a fourth lens element L4 of a positive meniscus configuration convex to the object side; a diaphragm ST; a third lens unit Gr3 including a first doublet lens element DL1 consisting of a fifth lens element L5 of a bi-convex configuration and a sixth lens element L6 of a bi-concave configuration; and a fourth lens unit Gr4 including a seventh lens element L7 of a positive meniscus configuration concave to the object side. On the image side of the fourth lens unit Gr4 of this zoom lens system, a plane-parallel plate LPF corresponding to the optical low-pass filter is disposed. In this embodiment, the first lens unit Gr1 and the second lens unit Gr2 have a negative optical power, and the third lens unit Gr3 and the fourth lens unit Gr4 have a positive optical power.

[0073] In this zoom lens system, in zooming from the shortest focal length condition to the longest focal length condition, the first lens unit Gr1 is fixed with respect to the image plane, the second lens unit Gr2 moves so as to draw a locus of a U-turn convex to the image side such that it first moves toward the image side and then moves toward the object side, the third lens unit Gr3 substantially monotonously moves toward the object side integrally with the diaphragm ST disposed on the object side of the third lens unit Gr3, the fourth lens unit Gr4 substantially monotonously moves toward the image side, and the plane-parallel plate LPF is fixed with respect to the image plane.

[0074] Of the lens surfaces, the object side surface of the second lens element L2, the image side surface of the third lens element L3, the image side surface of the fourth lens element L4, the image side surface of the sixth lens element L6 and both side surfaces of the seventh lens element L7 are aspherical.

[0075] A zoom lens system of the tenth embodiment comprises from the object side to the image side: a first lens unit Gr1 including a first lens element L1 being a negative meniscus lens element convex to the object side, and a plane PR corresponding to the prism; a second lens unit Gr2 including a second lens element L2 of a bi-concave configuration and a third lens element L3 of a positive meniscus configuration convex to the object side; a diaphragm ST; a third lens unit Gr3 including a first doublet lens element DL1 consisting of a fourth lens element L4 of a bi-convex configuration and a fifth lens element L5 of a bi-concave configuration; a fourth lens unit Gr4 including a sixth lens element L6 of a negative meniscus configuration concave to the object side; and a fifth lens unit Gr5 including a seventh lens element L7 of a bi-concave configuration. On the image side of the fifth lens unit Gr5 of this zoom lens system, a plane-parallel plate LPF corresponding to the optical low-pass filter is disposed. In this embodiment, the first lens unit Gr1 and the second lens unit Gr2 have a negative optical power, the third lens unit Gr3 and the fourth lens unit Gr4 have a positive optical power, and the fifth lens unit Gr5 has a negative optical power.

[0076] In this zoom lens system, in zooming from the shortest focal length condition to the longest focal length condition, the first lens unit Gr1 is fixed with respect to the image plane, the second lens unit Gr2 moves so as to draw a locus of a U-turn convex to the image side such that it first moves toward the image side and then moves toward the object side, the third lens unit Gr3 substantially monotonously moves toward the object side integrally with the diaphragm ST disposed on the object side of the third lens unit Gr3, the fourth lens unit Gr4 substantially monotonously moves toward the image side, and the fifth lens unit Gr5 is fixed with respect to the image plane together with the plane-parallel plate LPF disposed on the image side of the fifth lens unit Gr5.

[0077] Of the surfaces of the lens elements, the image side surface of the third lens element L3, the image side surface of the fourth lens element L4, the image side surface of the sixth lens element L6 and both side surfaces of the seventh lens element L7 are aspherical.

[0078] In the zoom lens systems of these embodiments, the prism PR having a reflecting surface that bends the optical axis of the object light substantially 90 degrees is provided in the first lens unit. By thus bending the optical axis of the object light substantially 90 degrees, the apparent thickness of the imaging device can be reduced.

[0079] When a digital camera is taken as an example, the element that takes up the largest volume in the apparatus is the imaging device including the zoom lens system. Particularly, when in digital cameras, optical elements such as lens elements and a diaphragm included in the zoom lens system are arranged in line without the direction of the optical axis being changed like in conventional lens-shutter type film-based cameras, the size of the camera in the direction of the thickness substantially depends on the distance from the most object side element of the zoom lens system to the image sensor included in the imaging device. However, the aberration correction level of imaging devices have dramatically improved with the increase in the number of pixels of image sensors in recent years. Consequently, the number of lens elements of the zoom lens systems included in imaging devices never stop increasing, so that because of the thickness of the lens elements, it is difficult to reduce the thickness even when the camera is not used (in so-called collapsed condition).

[0080] On the contrary, by adopting the structure that the optical axis of the object light is bent substantially 90 degrees by the reflecting surface like the zoom lens systems of the embodiments, the size of the imaging device in the direction of the thickness can be reduced to the distance from the most object side lens element to the reflecting surface when the camera is not used, so that the apparent thickness of the imaging device can be reduced. Moreover, by adopting the structure that the optical axis of the object light substantially 90 degrees by the reflecting surface, the optical path of the object light can be folded in the vicinity of the reflecting surface, so that space can be effectively used and further size reduction of the imaging device can be attained.

[0081] It is desirable that the reflecting surface be disposed in the first lens unit Gr1. By disposing the reflecting surface in the first lens unit Gr1 disposed on the most object side, the size of the imaging device in the direction of the thickness can be minimized.

[0082] It is desirable that the first lens unit Gr1 including the reflecting surface have a negative optical power. By the first lens unit Gr1 having a negative optical power, the size of the reflecting surface in the reflecting surface position can be reduced. Moreover, by adopting the structure that the first lens unit Gr1 has a negative optical power, the zoom lens system is of a so-called minus lead type. Minus lead type zoom lens systems are desirable because it is easy for them to adopt a retrofocus type structure in a wide focal length range and attain the image-side telecentricity necessary for optical systems for forming optical images on the image sensor.

[0083] While any of (a) an internal reflection prism (embodiments), (b) a surface reflection prism, (c) an internal reflection plane mirror and (d) a surface reflection mirror may be adopted as the reflecting surface, (a) an internal reflection mirror is the most suitable. By adopting an internal reflection prism, the object light passes through the medium of the prism, so that the axial distance when the object light passes through the prism is a reduced axial distance shorter than the normal air distance in accordance with the refractive index of the medium. For this reason, it is desirable that an internal reflection prism be adopted as the structure of the reflecting surface because an optically equivalent structure can be attained with a smaller space.

[0084] When the reflecting surface is an internal reflection prism, it is desirable that the material of the prism satisfy the following condition:

Np≧1.55  (1)

[0085] where Np is the refractive index of the material of the prism.

[0086] When the refractive index of the prism be lower than this range, the contribution to size reduction is small. Therefore, it is undesirable that the refractive index of the prism be lower than this range.

[0087] In addition to this range, it is desirable that the refractive index be within the following range:

Np≧1.7  (1)′

[0088] The reflecting surface is not necessarily a complete total reflection surface. The reflectance of part of the reflecting surface may be appropriately adjusted so that part of the object light branches off so as to be incident on a sensor for metering or distance measurement. Moreover, the reflectance of the entire area of the reflecting surface may be appropriately adjusted so that the finder light branches. While the incident surface and the exit surface of the prism are both plane in the embodiments, they may have an optical power.

[0089] It is desirable that not more than two lens elements be disposed on the object side of the reflecting surface. In a structure having in the first lens unit the prism PR having a reflecting surface that bends the optical axis of the object light substantially 90 degrees, the thickness of the optical system substantially depends on the distance from the object side surface of the lens element disposed on the most object side to the reflecting surface. Therefore, by disposing not more than two lens elements on the object side of the reflecting surface, a thin optical system can be obtained. In particular, when the first lens unit Gr1 includes only one lens element and the reflecting surface, the degree of freedom of the lens barrel structure can be increased, so that cost reduction of the imaging device can be attained. When the first lens unit Gr1 includes only two lens elements and the reflecting surface, relative decentration aberration correction can be performed, which is advantageous in optical performance.

[0090] Further, it is desirable that the first lens unit Gr1 be fixed with respect to the image plane during zooming. Since the first lens unit Gr1 includes the reflecting surface, moving it requires a large space, and in particular, when the reflecting surface comprises a prism, it is necessary to move a prism having a large weight, so that a heavy burden is placed on the driving mechanism. Moreover, by the first lens unit Gr1 being fixed with respect to the image plane during zooming, an optical system whose overall length does not vary can be obtained. Moreover, since the lens barrel structure can be simplified, cost reduction of the imaging device can be attained. Further, by adopting the structure that the first lens unit Gr1 is fixed during zooming, particularly in digital cameras, it is easy to initialize the control system for controlling the lens units movable during zooming, so that the time necessary for the camera to become ready to photograph when the main power is turned on can be reduced.

[0091] The zoom lens systems of the embodiments adopt a structure that the second lens unit Gr2 succeeding the first lens unit Gr1 having a negative optical power also has a negative optical power. This structure is desirable because it makes it easy to adopt the above-mentioned structure that the first lens unit Gr1 is fixed.

[0092] Next, conditions desirably satisfied by the embodiments will be described. It is to be noted that while the corresponding effect can be attained by satisfying any one of the conditions alone, it is more desirable that a plurality of conditions be satisfied from the viewpoint of optical performance and size reduction.

[0093] It is desirable that the zoom lens systems of the embodiments satisfy the following condition

0.5<|f1/f2|<5  (2)

[0094] where f1 is the focal length of the first lens unit Gr1 and f2 is the focal length of the second lens unit Gr2.

[0095] The condition (2) defines the desirable ratio between the focal lengths of the first lens unit Gr1 and the second lens unit Gr2. When the lower limit of the condition (2) is exceeded, since the focal length of the first lens unit Gr1 is too short, distortion (particularly the negative distortion in the shortest focal length condition) is extraordinary, so that it is difficult to secure excellent optical performance. When the upper limit of the condition (2) is exceeded, since the focal length of the first lens unit Gr1 is too long, the negative optical power of the first lens unit Gr1 is weak, so that the diameter of the first lens unit Gr1 increases, which is undesirable in view of size reduction.

[0096] Further, it is desirable that the zoom lens systems of the embodiments satisfy the following condition:

1.5<|f12w|/fw<4  (3)

[0097] where f12w is the composite focal length of the first lens unit Gr1 and the second lens unit Gr2 in the shortest focal length condition and fw is the overall focal length of the lens system in the shortest focal length condition.

[0098] The condition (3) relates to the composite focal length of the first lens unit Gr1 and the second lens unit Gr2 in the shortest focal length condition. When the upper limit of the condition (3) is exceeded, the overall length increases because the composite focal length of the first lens unit Gr1 and the second lens unit Gr2 is too long, and the lens diameter increases because the composite optical power of the first lens unit Gr1 and the second lens unit Gr2 is weak. Consequently, it is difficult to obtain a compact zoom lens system. When the lower limit of the condition (3) is exceeded, since the composite focal length of the first lens unit Gr1 and the second lens unit Gr2 is too short, the negative distortion generated in the first lens unit Gr1 and the second lens unit Gr2 is too large and difficult to correct in the shortest focal length condition.

[0099] Further, it is desirable that the zoom lens systems of the embodiments satisfy the following condition:

0.4<|f12w|/f3<1.5  (4)

[0100] where f12w is the composite focal length of the first lens unit Gr1 and the second lens unit Gr2 in the shortest focal length condition and f3 is the focal length of the third lens unit Gr3.

[0101] The condition (4) relates to the ratio between the composite focal length of the first lens unit Gr1 and the second lens unit Gr2 and the focal length of the third lens unit Gr3 in the shortest focal length. That the upper limit of the condition (4) is exceeded means that the composite focal length of the first lens unit Gr1 and the second lens unit Gr2 is relatively long. Therefore, it is undesirable that the upper limit of the condition (4) be exceeded because the position of the exit pupil shifts toward the image side. When the lower limit of the condition (4) is exceeded, since the composite focal length of the first lens unit Gr1 and the second lens unit Gr2 is too short, the negative distortion generated in the first lens unit Gr1 and the second lens unit Gr2 is too large and difficult to correct in the shortest focal length condition.

[0102] It is preferable that zoom lens system satisfy the following condition (5):

1.0<D/fw<2.6  (5)

[0103] where D represents an axial distance between surface at the most object side surface of the first lens unit and reflection surface; and fw represents a focal length of the entire zoom lens system in a wide angle condition.

[0104] The condition (5) defines the preferable relation the axial distance between surface at the most object side surface of the first lens unit and reflection surface. This condition (5) is required to miniaturize the entire optical system having reflection surface. If the lower limit of condition (5) were be transgressed, the optical power of the lens elements at the object side of the reflection surface would be too strong. This would cause a distortion so large (especially the negative distortion on the wide-angle end) that it would be impossible to secure satisfactory optical performance. By contrast, if the upper limit of condition (5) were to be transgressed, the axial distance between surface at the most object side surface of the first lens unit and reflection surface would be too long, which is undesirable in term of miniaturization. In addition to the above-mentioned range, it is preferable that the following range (5)′ is fulfilled:

D/fw<2.2  (5)′

[0105] While the lens units of the embodiments comprise only refractive type lens elements that deflect the incident ray by refraction (that is, lens elements of a type in which the incident ray is deflected at the interface between media having different refractive indices), the present invention is not limited thereto. For example, the lens units may comprise diffractive type lens elements that deflect the incident ray by diffraction, refractive-diffractive hybrid lens elements that deflect the incident ray by a combination of diffraction and refraction, or gradient index lens elements that deflect the incident ray by the distribution of refractive index in the medium.

[0106] The construction of the zoom lens systems included in the imaging device embodying the present invention will be more concretely described with reference to construction data, graphic representations of aberrations and the like. A first to a tenth example described here as examples corresponds to the first to the tenth embodiments described above. The lens construction views (FIGS. 1 to 10) showing the first to the tenth embodiments show the lens arrangements of the corresponding first to tenth examples.

[0107] In the construction data of the examples, ri (i=1,2,3, . . . ) is the radius (mm) of curvature of the i-th surface counted from the object side, di (i=1,2,3, . . . ) is the i-th axial distance (mm) counted from the object side, and Ni (i=1,2,3, . . . ) and vi (i=1,2,3, . . . ) are the refractive index (Nd) and the Abbe number (vd), to the d-line, of the i-th optical element counted from the object side. In the construction data, as the axial distances that vary during zooming, values in the shortest focal length condition (wide-angle limit, W), in the middle focal length condition (middle, M) and in the longest focal length condition (telephoto limit, T) are shown. The overall focal lengths (f, mm) and the f-numbers (FNO) in the focal length conditions (W), (M) and (T) are shown together with other data.

[0108] The surfaces whose radii of curvature ri are marked with asterisks are aspherical, and are defined by the following expression (AS) expressing the aspherical surface configuration. Aspherical data of the embodiments is shown as well. $\begin{matrix} {x = {\frac{C_{0}y^{2}}{1 + \sqrt{1 - {ɛ\quad C_{0}^{2}y^{2}}}} + {\sum{{Ai}\quad y^{i}}}}} & ({AS}) \end{matrix}$

[0109] where,

[0110] x represents the shape (mm) of the aspherical surface (i.e., the displacement along the optical axis at the heighty in a direction perpendicular to the optical axis of the aspherical surface),

[0111] Co represents the curvature (mm⁻¹) of the reference aspherical surface of the aspherical surface,

[0112] y represents the height in a direction perpendicular to the optical axis,

[0113] ε represents the quadric surface parameter, and

[0114] Ai represents the aspherical coefficient of order i.

EXAMPLE 1

[0115] f = 5.1-8.9-14.7 Fno. = 2.16-3.04-4.10 [Radius of [Axial [Refractive [Abbe Curvature] Distance] Index(Nd)] Number(νd)] r1 = 17.931  d1 =  1.000 N1 = 1.82302 ν1 = 36.21 r2 = 10.890  d2 =  3.800 r3 = ∞  d3 = 12.400 N2 = 1.84666 ν2 = 23.82 r4 = ∞  d4 =  1.500-3.379-1.696 r5* = −436.249  d5 =  1.000 N3 = 1.65461 ν3 = 46.54 r6* = 5.978  d6 =  1.270 r7 = 10.014  d7 =  1.656 N4 = 1.84666 ν4 = 23.82 r8 = 33.402  d8 = 11.535-4.725-1.020 r9 = ∞  d9 =  0.600 r10 = 6.649 d10 =  6.427 N5 = 1.75450 ν5 = 51.57 r11 = −7.769 d11 =  1.000 N6 = 1.84666 ν6 = 23.82 r12* = 30.896 d12 =  2.020-8.365-14.584 r13* = −21.319 d13 =  3.778 N7 = 1.52510 ν7 = 56.38 r14 = −5.800 d14 =  2.804-1.390-0.560 r15 = −11.316 d15 =  0.800 N8 = 1.48749 ν8 = 70.44 r16 = −32.669 d16 =  0.100 r17 = ∞ d17 =  2.000 N9 = 1.51680 ν2 = 64.20 r18 = ∞

[0116] [Aspherical Coefficient]

[0117] r5*

ε=0.10000000D+01

A4=0.95247363D−05

A6=0.44499878D−05

A8=0.20201509D−06

A10=0.15630434D−08

[0118] r6*

ε=0.10000000D+01

A4=−0.44138182D−03

A6=−0.17905680D−04

A8=−0.12106726D−06

A10=0.25333947D−07

[0119] r13*

ε=0.10000000D+01

A4=0.11420046D−02

A6=0.61304067D−04

A8=−0.24678605D−05

A10=0.38078980D−06

[0120] r14*

ε=0.10000000D+01

A4=−0.17175253D−02

A6=0.35415900D−04

A8=−0.51967472D−05

A10=0.10804669D−06

EXAMPLE 2

[0121] f = 5.1-8.9-14.7 Fno. = 2.16-2.97-4.10 [Radius of [Axial [Refractive [Abbe Curvature] Distance] Index(Nd)] Number(νd)] r1* = 77.048  d1 =  1.000 N1 = 1.66602 ν1 = 30.12 r2 = 10.412  d2 =  3.701 r3 = ∞  d3 = 12.400 N2 = 1.84666 ν2 = 23.82 r4 = ∞  d4 =  0.200 r5 = 12.063  d5 =  1.645 N3 = 1.84898 ν3 = 33.15 r6 = 22.797  d6 =  2.045-5.298-3.490 r7* = 74.513  d7 =  1.000 N4 = 1.52510 ν4 = 56.38 r8* = 6.297  d8 =  1.041 r9 = 7.766  d9 =  1.464 N5 = 1.79850 ν5 = 22.6  r10 = 10.311 d10 = 13.841-5.438-1.000 r11 = ∞ d11 =  0.600 r12 = 6.616 d12 =  5.892 N6 = 1.75450 ν6 = 51.57 r13 = −10.215 d13 =  1.000 N7 = 1.84666 ν7 = 23.82 r14* = 18.124 d14 =  2.079-8.055-15.451 r15* = −23.464 d15 =  3.400 N8 = 1.52510 ν8 = 56.82 r16 = −6.333 d16 =  2.476-1.650-0.500 r17 = 14.316 d17 =  1.000 N9 = 1.84833 ν9 = 29.89 r18 = 10.360 d18 =  0.907 r19 = ∞ d19 =  2.000 N10 = 1.51680  ν10 = 64.20  r20 = ∞

[0122] [Aspherical Coefficient]

[0123] r1*

ε=0.10000000E30 01

A4=0.63638407E31 04

A6=0.36516691E−06

A8=0.15861666E−08

[0124] r7*

ε=0.10000000E+01

A4=0.63173747E−03

A6=042880271E−04

A8=−0.13655536E−05

A10=0.17341485E−07

[0125] r8*

ε=0.10000000E+01

A4=−0.78352207E−03

A6=0.45124782E−04

A8=−0.17639048E−05

A10=0.22553499E−07

[0126] r15*

ε=0.10000000E+01

A4=0.10864595E−02

A6=0.63616957E−04

A8=−0.36734216E−05

A10=0.41688467E−06

[0127] r16*

ε=0.10000000E+01

A4=0.14356439E−02

A6=0.25426605E−04

A8=−0.32121190E−05

A10=0.95302924E−07

EXAMPLE 3

[0128] f = 4.5-7.9-12.9 Fno. = 2.1-2.8-3.7 [Radius of [Axial [Refractive [Abbe Curvature] Distance] Index(Nd)] Number(νd)] r1 = 4101.218  d1 =  0.700 N1 = 1.78589 ν1 = 44.20 r2 = 19.552  d2 =  0.900 r3 = ∞  d3 =  8.000 N2 = 1.84666 ν2 = 23.82 r4 = ∞  d4 =  1.000-3.596-1.000 r5* = 56.521  d5 =  0.800 N3 = 1.57501 ν3 = 41.49 r6* = 4.357  d6 =  1.021 r7 = 7.895  d7 =  1.6000 N4 = 1.84666 ν4 = 23.82 r8 = 21.921  d8 = 10.752-3.530-0.969 r9 = ∞  d9 =  0.650 r10 = 5.274 d10 =  4.755 N5 = 1.75450 ν5 = 51.57 r11 = −9.977 d11 =  0.010 N6 = 1.51400 ν6 = 42.83 r12 = −9.977 d12 =  0.800 N7 = 1.84666 ν7 = 23.82 r13* = 15.094 d13 =  2.179-7.261-12.815 r14* = −25.000 d14 =  3.200 N8 = 1.52510 ν8 = 56.38 r15* = −5.767 d15 =  1.453-0.996-0.600 r16 = 10.099 d16 =  0.983 N9 = 1.70055 ν9 = 30.11 r17 = 6.767 d17 =  0.948 r18 = ∞ d18 =  1.500 N10 = 1.51680  ν10 = 64.20  r19 = ∞

[0129] [Aspherical Coefficient]

[0130] r5*

ε=0.10000000E+01

A4=−0.44053024E−03

A6=−0.45582866E−04

A8=0.56807258E−05

A10=−0.21748168E−06

[0131] r6*

ε=0.10000000E+01

A4=−0.19077667E−02

A6=−0.45431102E−04

A8=−0.17609821E−05

A10=−0.26911785E−08

[0132] r13*

ε=0.10000000E+01

A4=0.24256912E−02

A6=0.13113475E−03

A8=−0.19935678E−05

A10=0.20427432E−05

[0133] r14*

ε=0.10000000E+01

A4=−0.76241384E−03

A6=−0.45684352E−04

A8=0.74367662E−05

A10=0.17395830E−06

[0134] r15*

ε=0.10000000E+01

A4=0.16617833E−02

A6=−0.97370809E−04

A8=0.83998804E−05

EXAMPLE 4

[0135] f = 4.5-7.6-12.9 Fno. = 2.1-2.8-2.97 [Radius of [Axial [Refractive [Abbe Curvature] Distance] Index(Nd)] Number(νd)] r1 = −25.000  d1 =  0.800 N1 = 1.63980 ν1 = 34.55 r2 = −115.843  d2 =  0.100 r3 = ∞  d3 =  9.200 N2 = 1.84666 ν2 = 23.82 r4 = ∞  d4 =  1.000-4.551-2.772 r5* = 21.359  d5 =  0.800 N3 = 1.83400 ν3 = 37.15 r6* = 5.824  d6 =  3.352 r7 = 14.337  d7 =  1.500 N4 = 1.84666 ν= 423.82 r8 = 52.503  d8 = 12.765-4.785-0.910 r9 = ∞  d9 =  0.700 r10 = 12.888 d10 =  2.200 N5 = 1.75450 ν5 = 51.57 r11 = −36.914 d11 =  0.100 r12 = 4.598 d12 =  3.800 N6 = 1.48749 ν6 = 70.44 r13 = 181.628 d13 =  0.010 N7 = 1.51400 ν7 = 42.83 r13 = 181.628 d14 =  1.000 N8 = 1.84666 ν8 = 23.82 r15* = 3.955 d15 =  1.500-6.298-12.506 r16* = 10.062 d16 =  2.000 N9 = 1.48749 ν9 = 70.44 r17* = −8.840 d17 =  1.472-1.104-0.600 r18 = ∞ d18 =  1.700 N10 = 1.51680  ν10 = 64.20  r19 = ∞

[0136] [Aspherical Coefficient]

[0137] r5*

ε=0.10000000E+01

A4=0.28920160E−03

A6=−0.24770223E−04

A8=0.40226114E−06

[0138] r6*

ε=0.10000000 E+01

A4=−0.28416506E−03

A6=−0.39127534E−04

A8=0.10049102E−06

[0139] r15*

ε=0.10000000E+01

A4=0.22971891E−02

A6=0.61362182E−04

A8=0.3054044E−04

[0140] r16*

ε=0.10000000 E+01

A4=0.29657551E−02

A6=−0.32988137E−03

A=0.18146796E−04

[0141] r17*

ε=0.10000000E+01

A4=0.65616586E−02

A6=−0.68518707E−03

A=0.33543925E−04

EXAMPLE 5

[0142] f = 4.5-7.9-12.9 Fno. = 2.1-2.89-3.8 [Radius of [Axial [Refractive Curvature] Distance] Index(Nd)] [Abbe Number(νd)] r1 = 16.688  d1 =  0.800 N1 = 1.54072 ν1 = 47.22 r2 = 7.343  d2 =  2.500 r3 = ∞  d3 =  8.400 N2 = 1.84666 ν2= 23.82 r4 = ∞  d4 =  1.500-2.971-1.500 r5* = 164.473  d5 =  0.800 N3 = 1.62004 ν3 = 36.26 r6* = 4.995  d6 =  1.353 r7 = 10.132  d7 =  2.267 N4 = 1.84666 ν4 = 23.82 r8 = 69.912  d8 = 11.101-4.724-0.862 r9 = ∞  d9 =  0.650 r10 = 5.681 d10 =  5.504 N5 = 1.75450 ν5 = 51.57 r11 = −10.007 d11 =  0.010 N6 = 1.51400 ν6 = 42.83 r12 = −10.007 d12 =  0.800 N7 = 1.84666 ν7 = 23.82 r13* = 13.518 d13 =  1.987-8.774-14.499 r14* = 72.616 d14 =  3.700 N8 = 1.52510 ν8 = 56.38 r15* = −8.793 d15 =  3.078-1.197-0.806 r16 = ∞ d16 =  1.500 N9 = 1.51680 ν9 = 64.20

[0143] [Aspherical Coefficient]

[0144] r5*

ε=0.10000000E+01

A4=−0.50212557E−03

A6=0.58262738E−04

A8=−0.45960476E−05

A10=0.10745067E−06

[0145] r6*

ε=0.10000000E+01

A4=−0.17341477E−02

A6=0.76117570E−04

A8=−0.99234139E−05

A10=0.25780579E−06

[0146] r13*

ε=0.10000000 E+01

A4=0.22365769E−02

A6=0.79579971E−04

A8=0.53500363E−05

A10=0.10651891E−05

[0147] r14*

ε=0.10000000E+01

A4=−0.74920577E−03

A6=−0.44003627E−04

A8=−0.46232075E−05

A10=0.52351697E−06

[0148] r15*

ε=0.10000000E+01

A4=0.27419718E−03

A6=−0.15545535E−03

A8=0.68734468E−03

EXAMPLE 6

[0149] f = 4.5-7.9-12.9 Fno. = 2.1-2.86-3.78 [Radius of [Axial [Refractive Curvature] Distance] Index(Nd)] [Abbe Number(νd)] r1 = 131.891  d1 =  0.800 N1 = 1.51742 ν1 = 52.41 r2 = 11.659  d2 =  1.650 r3 = ∞  d3 =  8.000 N2 = 1.84666 ν2 = 23.82 r4 = ∞  d4 =  1.500 r5* = 35.321  d5 =  0.800 N3 = 1.52200 ν3 = 52.20 r6* = 4.893  d6 =  1.276 r7 = 7.568  d7 =  2.000 N4 = 1.84666 ν4 = 23.82 r8 = 12.453  d8 = 11.029-3.671-0.998 r9 = ∞  d9 =  0.6500 r10 = 5.991 d10 =  4.909 N5 = 1.75450 ν5 = 51.57 r11 = −9.320 d11 =  0.010 N6 = 1.51400 ν6 = 42.83 r12 = −9.320 d12 =  1.400 N7 = 1.84666 ν7 = 23.82 r13* = 26.705 d13 =  1.370-6.910-12.832 r14* = −16.667 d14 =  3.678 N8 = 1.52510 ν8 = 56.38 r15* = −6.042 d15 =  4.129-3.385-2.697 r16 = ∞ d16 =  1.500 N9 = 1.51680 ν9 = 64.20 r17 = ∞

[0150] [Aspherical Coefficient]

[0151] r5*

ε=0.10000000E+01

A4=0.43313297E−03

A6=−0.10070798E−03

A8=0.84126830E−05

A10=−0.26384097E−06

[0152] r6*

ε=0.10000000E+01

A4=−0.30789841E−03

A6=−0.11170196E−03

A8=0.66705245E−05

A10=−0.24941305E−06

[0153] r13*

ε=0.10000000 E+01

A4=0.15633769E−02

A6=0.51050129E−04

A8=0.24266581E−06

A10=0.67988002E−06

[0154] r14*

ε=0.10000000E+01

A4=−0.12218564E−02

A6=0.25134426E−03

A8=−0.53931767E−04

A10=0.43794302E−05

[0155] r15*

ε=0.10000000E+01

A4=0.94953834E−03

A6=−0.27258786E−04

A8=0.28920117E−05

EXAMPLE 7

[0156] f = 4.5-7.9-12.9 Fno. = 2.0-2.85-3.74 [Radius of [Axial [Refractive [Abbe Curvature] Distance] Index(Nd)] Number(νd)] r1 = 33.725  d1 =  0.800 N1 = 1.85000 ν1 = 40.04 r2 = 11.351  d2 =  1.200 r3 = 25.554  d3 =  1.458 N2 = 1.75450 ν2 = 51.57 r4 = 37.693  d4 =  0.800 r5 = ∞  d5 =  8.200 N3 = 1.84666 ν3 = 23.82 r6 = ∞  d6 =  1.500-3.420-1.500 r7 = 97.822  d7 =  0.800 N4 = 1.52510 ν4 = 56.38 r8* = 5.111  d8 =  0.743 r9 = 6.467  d9 =  2.000 N5 = 1.84666 ν5 = 23.82 r10 = 10.975 d10 = 10.550-4.249-1.028 r11 = ∞ d11 =  0.650 r12 = 6.194 d12 =  5.604 N6 = 1.75450 ν6 = 51.57 r13 = −6.781 d13 =  0.010 N7 = 1.51400 ν7 = 42.83 r14 = −6.781 d14 =  1.183 N8 = 1.84666 ν8 = 23.82 r15* = 38.043 d15 =  3.186-8.555-13.974 r16* = −16.667 d16 =  3.812 N9 = 1.77250 ν9 = 49.77 r17* = −5.893 d17 =  2.712-1.724-1.447 r18 = ∞ d18 =  1.500 N10 = 1.51680  ν10 = 64.20  r19 = ∞

[0157] [Aspherical Coefficient]

[0158] r8*

ε=0.10000000E+01

A4=−0.15428275E−03

A6=−0.42877249E−04

A8=0.15793970E−06

A10=−0.20720675E−07

[0159] r10*

ε=0.10000000E+01

A4=−0.64995991E−04

A6=0.17099407E−04

A8=−0.16152162E−07

[0160] r15*

ε=0.10000000E+01

A4=0.13775987E−02

A6=0.47166979E−04

A8=0.20857832E−05

A10=0.23955123E−06

[0161] r16*

ε=0.10000000E+01

A4=−0.20963217E−02

A6=0.74122201E−04

A8=−0.11877575E−04

A10=0.53768544E−06

[0162] r17*

ε=0.10000000E+01

A4=0.80770597E−04

A6=0.42148914E−05

A8=0.60309537E−07

EXAMPLE 8

[0163] f = 4.5-7.9-12.9 Fno. = 2.0-2.81-3.67 [Radius of [Axial [Refractive [Abbe Curvature] Distance] Index(Nd)] Number(νd)] r1 = 15.797  d1 =  0.800 N1 = 1.58913 ν1 = 61.11 r2 = 7.557  d2 =  2.700 r3 = ∞  d3 =  8.009 N2 = 1.84666 ν2 = 23.82 r4 = ∞  d4 =  1.500-3.160-1.500 r5 = −26.368  d5 =  0.800 N3 = 1.48749 ν3 = 70.44 r6* = 4.708  d6 =  0.518 r7 = 5.361  d7 =  2.154 N4 = 1.85000 ν4 = 40.04 r8* = 10.802  d8 = 11.235-4.910-1.331 r9 = ∞  d9 =  0.650 r10 = 6.699 d10 =  4.000 N5 = 1.75450 ν5 = 51.57 r11 = −9.744 d11 =  0.010 N6 = 1.51400 ν6 = 42.83 r12 = −9.744 d12 =  0.800 N7 = 1.79850 ν7 = 22.60 r13 = 67.530 d13 =  0.537 r14 = 28.497 d14 =  0.800 N8 = 1.58340 ν8 = 30.23 r15* = 18.947 d15 =  2.612-8.560-14.167 r16* = −30.752 d16 =  4.200 N9 = 1.52510 ν9 = 56.38 r17* = −5.241] d17 =  2.934-1.651-1.283 r18 = ∞ d18 =  1.500 N10 = 1.51680  ν10 = 64.20  r19 = ∞

[0164] [Aspherical Coefficient]

[0165] r6*

ε=0.10000000E+01

A4=−0.10145481E−02

A6=0.72075706E−04

A8=0.19174089E−05

A10=−0.46087898E−07

[0166] r8*

ε=0.10000000E+01

A4=0.70130028E−03

A6=0.46972417E−04

A8=0.33943302E−05

[0167] r15*

ε=0.10000000E+01

A4=0.14752106E−02

A6=0.55770047E−04

A8=−0.10845300E−05

A10=0 0.44294001E−06

[0168] r16*

ε=0.10000000E+01

A4=−0.18942226E−02

A6=0.69566995E−04

A8=−0.13206893E−04

A10=0.73140343E−06

[0169] r17*

ε=0.10000000E+01

A4=0.74167453E−03

A6=−0.16789975E−04

A8=0.14074200E−05

EXAMPLE 9

[0170] f = 4.5-7.9-12.9 Fno. = 2.0-2.88-3.77 [Radius of [Axial [Refractive [Abbe Curvature] Distance] Index(Nd)] Number(νd)] r1 = 24.847  d1 =  0.800 N1 = 1.85026 ν1 = 32.15 r2 = 9.507  d2 =  1.200 r3* = 18.529  d3 =  1.878 N2 = 1.52200 ν2 = 52.20 r4 = 37.877  d4 =  0.800 r5 = ∞  d5 =  8.200 N3 = 1.84666 ν3 = 23.82 r6 = ∞  d6 =  1.500-3.255-1.500 r7 = −23.840  d7 =  0.800 N4 = 1.52200 ν4 = 52.20 r8* = 5.612  d8 =  0.500 r9* = 6.897  d9 =  2.300 N5 = 1.84666 ν5 = 23.82 r10* = 17.332 d10 = 11.012-4.659-1.072 r11 = ∞ d11 =  0.650 r12 = 6.160 d12 =  6.000 N6 = 1.75450 ν6 = 51.57 r13 = −6.615 d13 =  0.010 N7 = 1.51400 ν7 = 42.83 r14 = −6.615 d14 =  0.969 N8 = 1.84666 ν8 = 23.82 r15* = 29.536 d15 =  1.496-7.489-12.982 r16* = −31.130 d16 =  4.200 N9 = 1.52510 ν9 = 56.38 r17* = −5.934 d17 =  3.226-1.831-1.680 r18 = ∞ d18 =  1.500 N10 = 1.51680  ν10 = 64.20  r19 = ∞

[0171] [Aspherical Coefficient]

[0172] r3*

ε=0.10000000E+01

A4=0.11455958E−03

A6=−0.33371789E−06

A8=0.16291474E−07

[0173] r8*

ε=0.10000000E+01

A4=0.11930738E−03

A6=−0.41125994E−04

A8=0.93638465E−06

A9=−0.22174114E−07

[0174] r10*

ε=0.10000000E+01

A4=−0.62127445E−04

A6=0.14433401E−04

A8=−0.23787289E−06

[0175] r15*

ε=0.10000000E+01

A4=0.15502859E−02

A6=0.47738830E−04

A8=0.42055482E−05

A10=0.17243267E−06

[0176] r16*

ε=0.10000000E+01

A4=−0.17058224E−02

A6=0.76334079E−04

A8=−0.14552475E−04

A10=0.69411194E−06

[0177] r17*

ε=0.10000000E+01

A4=0.88231293E−04

A6=−0.18063594E−04

A8=0.70394395E−06

EXAMPLE 10

[0178] f = 4.5-7.9-12.9 Fno. = 2.0-2.69-3.45 [Radius of [Axial [Refractive [Abbe Curvature] Distance] Index(Nd)] Number(νd)] r1 = 29.225  d1 =  0.800 N1 = 1.58913 ν1 = 61.11 r2 = 9.824  d2 =  2.288 r3 = ∞  d3 =  8.000 N2 = 1.84666 ν2 = 23.82 r4 = ∞  d4 =  1.500-4.764-1.500 r5 = 37.705  d5 =  0.800 N3 = 1.48749 ν3 = 70.44 r6* = 4.423  d6 =  0.500 r7 = 5.513  d7 =  2.00 N4 = 1.85000 ν4 = 40.04 r8* = 8.515  d8 = 12.201-3.853-1.149 r9 = ∞  d9 =  0.650 r10 = 6.604 d10 =  4.885 N5 = 1.75450 ν5 = 51.57 r11 = −7.480 d11 =  0.010 N6 = 1.51400 ν6 = 42.83 r12 = −7.480 d12 =  0.800 N7 = 1.79850 ν7 = 22.60 r13 = −19.278 d13 =  0.900-1.200-1.501 r14 = −7.554 d14 =  0.800 N8 = 1.58340 ν8 = 30.23 r15* = 153.332 d15 =  2.658-7.442-13.108 r16* = 7.127 d16 =  4.046 N9 = 1.52510 ν9 = 56.38 r17* = −66.811 d17 =  1.000 r18 = ∞ d18 =  1.500 N10 = 1.51680  ν10 = 64.20  r19 = ∞

[0179] [Aspherical Coefficient]

[0180] r6*

ε=0.10000000E+01

A4=−0.13188674E−03

A6=−0.11077449E−03

A8=0.36905376E−05

A10=0.29138999E−06

[0181] r8*

ε=0.10000000E+01

A4=−0.72069648E−04

A6=0.45751204E−04

A8=0.72652405E−06

[0182] r15*

ε=0.10000000E+01

A4=0.15958174E−02

A6=−0.11349576E−04

A8=0.19068718E−04

A10=0.94307372E−06

[0183] r16*

ε=0.10000000E+01

A4=−0.20231807E−03

A6=0.92943008E−04

A8=−0.39179305E−05

A10=0.15776897E−06

[0184] r17*

ε=0.10000000E+01

A4=0.11215385E−02

A6=0.29269875E−04

A8=0.12347517E−04

[0185]FIGS. 11A to 11I through 20A to 20I which are graphic representations of aberrations of the first to the tenth examples show aberrations of the zoom lens systems of the examples in in-focus state at infinity. In these figures, (W), (M) and (T) show aberrations (from the left, spherical aberration, sine condition, astigmatism and distortion; Y′(mm) is the maximum image height [corresponding to the distance from the optical axis] on the image sensor) in the shortest focal length condition, in the middle focal length condition and in the longest focal length condition, respectively. In the graphic representations of spherical aberration, the solid line (d) shows spherical aberration to the d-line, the chain line (g) shows spherical aberration to the g-line, the chain double-dashed line (c) shows spherical aberration to the c-line, and the broken line (SC) shows sine condition. In the graphic representations of astigmatism, the broken line (DM) shows astigmatism on the meridional image plane, and the solid line (DS) shows astigmatism on the sagittal image plane. In the graphic representations of distortion, the solid line shows distortion % to the d-line.

[0186] As described above, according to the zoom lens systems of the embodiments, an imaging device can be provided that is compact although having a high-performance and high-magnification zoom lens system.

[0187] Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be understood that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modification depart from the scope of the present invention, they should be construed as being included therein. 

What is claimed is:
 1. An imaging device comprising: a zoom lens system having a plurality of lens units and forming an optical image of an object so as to continuously optically zoom by varying distances between the lens unit; and an image sensor converting the optical image formed by the zoom lens system to an electric signal, wherein the zoom lens system comprises from an object side: a first lens unit being overall negative and including a reflecting surface that bends a luminous flux substantially 90 degrees; and a second lens unit disposed with a variable air distance from the first lens unit, and having a negative optical power.
 2. An imaging device as claimed in claim 1, wherein the first lens unit includes a right-angle prism having an internal reflecting surface as the reflecting surface.
 3. An imaging device as claimed in claim 2, wherein the following condition is satisfied: Np≧1.55 where Np is a refractive index to a d-line of the right-angle prism.
 4. An imaging device as claimed in claim 1, the zoom lens system further comprises, a third lens unit disposed with a variable air distance from the second lens unit, and having a positive optical power, a fourth lens unit disposed with a variable air distance from the third lens unit, and having a positive optical power.
 5. An imaging device as claimed in claim 4, wherein the zoom lens system consists of said first through fourth lens units.
 6. An imaging device as claimed in claim 4, the zoom lens system further comprising: a fifth lens unit disposed with a variable air distance from the fourth lens unit.
 7. An imaging device as claimed in claim 1,wherein, the first lens unit is fixed with respect to the image plane in zooming from the shortest focal length condition to the longest focal length condition.
 8. An imaging device as claimed in claim 1, wherein, the second lens unit moves so as to draw a locus of a U-turn convex to the image side in zooming from the shortest focal length condition to the longest focal length condition.
 9. An imaging device as claimed in claim 1, wherein the zoom lens system has not more than two lens elements disposed on the object side of the reflecting surface.
 10. An imaging device as claimed in claim 9, wherein the zoom lens system has only one lens element disposed on the object side of the reflecting surface.
 11. An imaging device as claimed in claim 1, wherein the zoom lens system fulfills the following condition: 0.5<|f1/f2|<5 where f1 is the focal length of the first lens unit and f2 is the focal length of the second lens unit.
 12. An imaging device as claimed in claim 1, wherein the zoom lens system fulfills the following condition: 1.5<|f12w|/fw<4 where f12w is the composite focal length of the first lens unit and the second lens unit in the shortest focal length condition and fw is the overall focal length of the lens system in the shortest focal length condition.
 13. An imaging device as claimed in claim 1, wherein the zoom lens system fulfills the following condition: 0.4<|f12w|f3<1.5 where f12w is the composite focal length of the first lens unit and the second lens unit in the shortest focal length condition and f3 is the focal length of the third lens unit.
 14. An imaging device as claimed in claim 1, wherein the zoom lens system fulfills the following condition: 1.0<D/fw<2.6 where D represents an axial distance between surface at the most object side surface of the first lens unit and reflection surface; and fw represents a focal length of the entire zoom lens system in a wide angle condition.
 15. A camera comprising: an imaging device having a zoom lens system a plurality of lens units and forming an optical image of an object so as to continuously optically zoom by varying distances between the lens unit and an image sensor converting the optical image formed by the zoom lens system to an electric signal, wherein the zoom lens system comprises from an object side: a first lens unit being overall negative and including a reflecting surface that bends a luminous flux substantially 90 degrees; and a second lens unit disposed with a variable air distance from the first lens unit, and having a negative optical power.
 16. A camera as claimed in claim 15, wherein the first lens unit includes a right-angle prism having an internal reflecting surface as the reflecting surface.
 17. A camera as claimed in claim 15, the zoom lens system further comprises, a third lens unit disposed with a variable air distance from the second lens unit, and having a positive optical power, a fourth lens unit disposed with a variable air distance from the third lens unit, and having a positive optical power.
 18. A camera as claimed in claim 15, wherein, the first lens unit is fixed with respect to the image plane in zooming from the shortest focal length condition to the longest focal length condition.
 19. A camera as claimed in claim 15, wherein, the second lens unit moves so as to draw a locus of a U-turn convex to the image side in zooming from the shortest focal length condition to the longest focal length condition.
 20. A camera as claimed in claim 15, wherein the zoom lens system has not more than two lens elements disposed on the object side of the reflecting surface.
 21. A camera as claimed in claim 15, wherein the zoom lens system fulfills the following condition: 0.5<|f1/f2|<5 where f1 is the focal length of the first lens unit and f2 is the focal length of the second lens unit.
 22. A camera as claimed in claim 15, wherein the zoom lens system fulfills the following condition: 1.5<|f12w|/fw<4 where f12w is the composite focal length of the first lens unit and the second lens unit in the shortest focal length condition and fw is the overall focal length of the lens system in the shortest focal length condition.
 23. A camera as claimed in claim 15, wherein the zoom lens system fulfills the following condition: 0.4<|f12w|/f3 <1.5 where f12w is the composite focal length of the first lens unit and the second lens unit in the shortest focal length condition and f3 is the focal length of the third lens unit.
 24. A camera as claimed in claim 15, wherein the zoom lens system fulfills the following condition: 1.0<D/fw<2.6 where D represents an axial distance between surface at the most object side surface of the first lens unit and reflection surface; and fw represents a focal length of the entire zoom lens system in a wide angle condition. 